Those who write the histories of the twenty-first century will, I suspect, list an address delivered at a German university on this day ten years ago as one of this century’s most important speeches. In just 4,000 words, what we now call the “Regensburg Address” managed to identify the inner pathology that is corroding much of the world, how this malignancy emerged, and what can be done to address it.

The fact that it was the Roman Pontiff who showed how a collapse of faith in full-bodied conceptions of reason explains so much of our world’s evident disarray probably made Voltaire roll over in his grave. But Benedict XVI’s analysis—which enraged many Muslims but also drew scorn from some secular and religious progressives—didn’t emerge from a vacuum. The need to defend an understanding of reason that goes beyond the natural and social sciences has long featured in Joseph Ratzinger’s writings.

For what is at stake, Ratzinger believes, is nothing less than humanity’s ability to know the truth. And if man is defined as not just the one who knows, but as the one who knows that he knows, any faltering in his confidence that human reason can know truth that is more than empirical not only leads to the dead ends of fideism or sentimentalism. It obliterates man’s very distinctiveness. At the same time, recovering this confidence in reason has never, for Ratzinger, been about turning the clock back to a pre-Enlightenment world. In many ways, it’s about saving modernity from itself by opening its mind to the full grandeur of reason and, ultimately, the First Cause from which all else proceeds.

Knowing Enlightenment

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Given his reputation as a “conservative,” many people are surprised to learn that Ratzinger has never expressed hostility in principle to the Enlightenment. Ratzinger is certainly steeped in pre-modern sources such as the Scriptures. Nonetheless his mind is, in many ways, thoroughly modern. Though his Regensburg commentary begins by analyzing correspondence between a medieval Byzantine emperor and his Persian interlocutor, the majority of Ratzinger’s writings on the crisis of reason take the various Enlightenments as their starting point.

In a 1998 essay entitled “Faith between Reason and Feeling,” Ratzinger begins by outlining a 1927 conversation among three future Nobel physicists: Werner Heisenberg, Wolfgang Pauli, and Paul Dirac. Their subject matter was Albert Einstein’s conception of God and the conviction of another Nobel physicist, Max Planck, that “there was no conflict between science and religion.” According to Ratzinger, Heisenberg believed that the lack of conflict proceeded from a conviction that science was concerned with what is “true and false.” Religion, by contrast, was about “good and bad.” Science was “objective.” Religion was “subjective”—a matter of “taste,” as liberal Christianity’s Prussian progenitor, Friedrich Schleiermacher, put it.

Nevertheless, Ratzinger points out, Heisenberg expressed misgivings about whether humanity can survive such a division between “knowledge and faith.” In other words, the scientist—the Enlightenment figure par excellence—recognized that if “faith” primarily concerns subjective experiences and if “knowledge” is reduced to what is empirically verifiable, we have a major problem. At this point, Ratzinger notes, Wolfgang Pauli interjected that such a division means that “things will happen that are more frightful than anything we can yet imagine.” In the tone of one who lived through it, Ratzinger comments that a few years after this conversation occurred, “the unholy twelve years would begin.”

At no point does Ratzinger’s analysis demean the empirical method or question the scientific enterprise’s nobility. “Reason,” he states, “that operates in specialized areas in fact gains enormously in strength and capability.” Instead Ratzinger uses the ruminations of civilized, enlightened men to illustrate that once you reduce reason to these parameters, faith—but also philosophy and politics—collapses into emotivism and unreason. Welcome to the pseudo-religious madness of National Socialism and Marxism. Likewise, science ceases to be guided by what is reasonable. Welcome to the efficient destruction of European Jewry, medical experiments on Catholic priests in Dachau, and the systematic use of terror by Communist regimes to destroy opponents.

Restoring Faith in Reason

In Ratzinger’s view, part of the problem is that many Enlightenment thinkers actually didn’t have enough faith in reason. Technical knowledge certainly matters. The natural and social sciences that acquired such traction in the eighteenth century have helped subsequent generations live longer and healthier lives. Thanks in part to Adam Smith, millions continue to be liberated from material poverty.

The problem, Ratzinger states, is that many who take pride in their reasonability “no longer offer any perspective on the fundamental questions of mankind.” Why? Because by themselves, scientific and economic reasoning can’t explain why, for instance, we should want to cure disease or reduce poverty.

The same critique, Ratzinger adds, applies to some people of faith. Having accepted reason’s reduction to the empirical, they “sought a new sphere for religion.” “That,” Ratzinger maintains, “is why ‘feeling’ was assigned to [religion] as its own domain within human existence.” One is reminded of Faust’s response to Gretchen’s question about the nature of religion: “Feeling is all. The rest is just smoke and mirrors.”

The effects of this turn have been catastrophic for Christianity, which has long valued reason. In some instances, it reduces religious faith to fideism: what Ratzinger once defined as “the desire to believe against reason.” Many Christians no longer consider it necessary to “always be ready to give an explanation to anyone who asks you for a reason for your hope” (1 Peter 3:15). Just feel and believe!

But having ceased proposing Christian faith’s reasonability, some believers also start making basic errors in logic and methodology. The historical-critical study of the Bible, for example, becomes understood as the truly scientific way of comprehending these texts. Yet this method rules out, a priori, the notion that it is reasonable to believe in the truth of the miracles recorded in the Gospels if we recognize that a reasonable and loving God who is involved in human affairs may have good reasons to suspend the laws of nature in order to attest to truth. Absent this reasonable supposition, Christ’s miracles are quickly interpreted as “metaphors,” despite the Gospels’ insistence that these were real events witnessed by real flesh-and-blood people and thus should not be understood as akin to Greek mythology.

True Reason, True Knowledge

This brings us to the third dimension of Ratzinger’s thinking on these matters. How can we reassert reason’s fullness in the realms of science and religion in an age in which emotions and empirical inquiry are widely viewed as the primary reference points for discussion?

Ratzinger’s first suggestion is that we must rehabilitate reason in the world bequeathed by the Enlightenment. Those working in the natural sciences, for example, should be reminded that their disciplines rest on a philosophical foundation. “All our ideas about natural sciences and all practical applications,” Ratzinger writes, “are based on the assumption that the world is ordered according to rational, spiritual laws, [and] is imbued with rationality that can be traced out and copied by our reason.” Without this assumption, the scientific enterprise would never have gotten underway.

The same reasonable assumption raises the question of where this rationality came from in the first place. Answering that question might not take you immediately into the realm of the Scriptures, but it will lead you into natural theology. As Ratzinger asked in a 1999 paper delivered at the Sorbonne, “can reason really renounce its claim to the priority of reason over the irrational, the claim that the Logos is at the ultimate origin of things, without abolishing itself?”

This attention to God as Logos is crucial to Ratzinger’s second recommendation. Religions that once took reason seriously need to do so again. On one level, that translates into a call for a renewal of natural law reasoning within these religious communities.

Yet this isn’t where the bulk of Ratzinger’s emphasis has fallen. Instead Ratzinger devotes more attention to stressing Christianity’s need to demonstrate that it is the reasonable faith that provides access to full knowledge of the truth. Again, Ratzinger doesn’t dispense with the Enlightenment emphasis on reason. Instead, he responds to the classic challenge posed by the Age of Reason: to subject truth-claims to reason’s critical scrutiny.

Responding to that challenge, Ratzinger’s writings consistently take us through the Scriptures and Church Fathers to demonstrate that the God who reveals Himself to Abraham, and who Christians believe is fully revealed in the person of Christ, is truly the Logos. Here Ratzinger brings to bear his two favorite sources. “According to Augustine and the biblical tradition,” Ratzinger writes, “Christianity is not based on mythical images and vague notions that are ultimately justified by their political usefulness; rather, it relates to that divine presence which can be perceived by the rational analysis of reality.” This is what Christianity’s earliest adherents in the Roman Empire meant when they proclaimed their faith to be the religio vera: the religion of the truth first revealed to the Hebrews but now universalized for all as sure and liberating knowledge. Thus, Ratzinger says, “In Christianity, enlightenment has become part of religion and is no longer its opponent.”

Intellego ut Credam

It’s telling that in one of his last public addresses, in the midst of the chaos that engulfed his papacy in its final months, Ratzinger returned to these themes. Though visibly tired and clearly feeling his age, Ratzinger stated that he wanted “to reflect on the reasonableness of faith in God.”

Not only did Ratzinger reiterate the need to reject fideism, the type of faith that leads one to fly planes into buildings or cut the throat of an elderly priest, but he also underscored that reason confirms what revelation tells us to be true about God. Echoing Paul’s Letter to the Romans, Ratzinger specified that “reason is able to know with certainty that God exists through the creation.” It is this confidence, Ratzinger says, that “unfolds the horizons” for scientific discovery.

None of this is to downplay the scale of the challenge that Joseph Ratzinger identified so dramatically ten years ago at Regensburg. It means knitting back together a world in which reason points to true faith. It also involves helping the natural and social sciences, so stimulated by the various Enlightenments, to recognize their need for grounding in those truths that provide them with their very rationale and prevent them from being turned against man himself.

It would be easy, even understandable, to leave such tasks to another generation—one perhaps less awash in sentimental humanitarianism and less speechless in the face of the violent fideism currently plaguing the earth. That, however, was not Ratzinger’s way. To identify the pathologies of faith and reason that characterize the Muslim world and the West, he was willing to pay a high price in terms of rage from fideists and contempt from many who consider themselves enlightened.

The question we should ask ourselves is: are we willing to do the same?